Endless belt with automatic steering control

Abstract

Automatic tracking of an endless belt, such as a coated abrasive belt, is provided by fitting the belt with at least one permanent magnet, preferably of a flexible, rubber bonded sheet-like variety such as is conveniently adhered to the backside of the belt. One or more magnetic sensors positioned transversely to a longitudinal line defined by the path of the magnets as the belt is driven between rollers detect the magnets in the event the belt exceeds an allowed extent of transverse movement, in which event a control signal is generated which activates a steering mechanism causing the belt to move in the opposite transverse direction.

Having thus described the present invention, what is claimed is: 
     
       1. In a grinding machine utilizing an endless coated abrasive belt, a plurality of spaced and aligned rollers for supporting said belt, one of said rollers being movably supported to control the transverse position of the belt with respect to a path about the rollers, drive means for moving said position controlling roller, and sensing means for sensing movement of the belt transverse to its length and for providing a transverse movement signal indicative of the direction of transverse motion to the drive means to cause movement of said position controlling roller such as to impart transverse movement of the belt in a direction opposite to the sensed direction, wherein said sensing means comprises: at least one permanent magnet comprising a flexible magnet material including domain sized particles supported by a polymeric binder, said magnet being a part of the belt, movable with the belt, and being positioned such that the poles thereof exhibit a given orientation with respect to an edge of the belt,   magnetic field sensing means positioned adjacent the path of the magnet on the belt for responding to a change in the field provided by a said magnet as a result of transverse movement of the belt and for providing said transverse movement signal indicative of the direction of said transverse movement, and   means responsive to said transverse movement signal for controllably energizing said drive means to impart a reverse transverse movement to said belt.   
     
     
       2. A grinding machine according to claim 1 wherein said sensing means includes a pair of sensors spaced apart a distance defining an allowed extent of transverse excursion and wherein a single magnet is provided on said belt, said sensors being positioned on both sides of said magnet such that a signal is induced in either of the sensors upon movement of the magnet adjacent that sensor. 
     
     
       3. A grinding machine according to claim 1 wherein said sensing means includes a pair of sensors and said belt includes a pair of magnets, the allowable extent of transverse exclusion of said belt being defined by the difference between the separation between the pair of sensors and the separation between the pair of magnets. 
     
     
       4. An endless coated abrasive belt comprising a backing having on one side thereof a layer of abrasive granules, said belt having as a part thereof at least one discrete permanent magnet affixed adjacent at least one edge of the belt and movable therewith, said magnet extending over short lengths thereof such that the longitudinal dimension of the belt is substantially free of said magnet, and comprising a flexible magnet material including domain sized particles supported by a polymeric binder and being positioned such that the poles thereof exhibit a given orientation with respect to an edge of the belt to enable detection of movement of the belt in either direction transverse to its length to enable control over the transverse position of the belt. 
     
     
       5. An abrasive belt according to claim 4 wherein said material is shaped as a thin strip having a thickness not greater than 0.03 inch (0.8 mm) and a width not greater than 0.5 inch (12 mm). 
     
     
       6. An abrasive belt according to claim 4, comprising a flexible magnet adhered to backside of the backing. 
     
     
       7. An abrasive belt according to claim 4 wherein the poles of said magnet are aligned transverse to one edge of the belt. 
     
     
       8. An abrasive belt according to claim 4 wherein the poles of said magnet are aligned parallel to one edge of the belt. 
     
     
       9. An abrasive belt according to claim 4 wherein the poles of said magnet are aligned perpendicular to the surface of the belt. 
     
     
       10. An abrasive belt according to claim 4 further comprising as a part thereof at least a second permanent magnet movable with the belt, each of said magnets being positioned adjacent an opposite edge of the belt. 
     
     
       11. An abrasive belt according to claim 10 wherein the poles of both of said magnets are oriented normal to the surface of the belt. 
     
     
       12. An abrasive belt according to claim 11 wherein the poles of both of said magnets exhibit a like polarity. 
     
     
       13. An abrasive belt according to claim 11 wherein the polarity of the poles of the first magnet is opposite that of the second magnet. 
     
     
       14. A method of controlling the transverse position of an endless belt during movement thereof between a drive and support roller respectively, comprising the steps of (a) providing said endless belt with at least one permanent magnet comprising a flexible magnet material including domain sized particles supported by a polymeric binder, and positioning said magnet on said belt such that the magnetic poles exhibit a given orientation with respect to an edge of the belt;   (b) detecting a change in the magnetic field provided by a said magnet as a result of transverse movement of the belt and providing a transverse movement signal indicative of the direction of said transverse movement, and   (c) responding to said transverse motion signal to controllably energize at least one of said rollers to alter the axial alignment thereof, thereby controlling the transverse position of the belt.